Petroleum jelly or petrolatum is a well-known product that has many utilities, including cosmetic-related utilities. Petroleum jelly is an anhydrous semi-solid mixture of hydrocarbons, generally having carbon numbers greater than 25 and a melting-point usually within a few degrees of 75° C. (167° F.). It is colorless, or of a pale yellow color (when not highly distilled), translucent, and devoid of taste and smell when pure. It does not oxidize on exposure to air and is relatively inert. It is insoluble in water and soluble in several organic solvents. Although this product has been found to have many utilities, if prepared improperly, it has been found to contain toxic compounds, including polycyclic aromatic hydrocarbons (PAHs) linked to cancer. As a result, the European Union has classified petrolatum as a carcinogen and restricts its use in cosmetics. Moreover, petrolatum is not extensively used in cosmetic products due to its “greasy feel” on the skin.
Very few non-hydrocarbon-based gels have also been developed for use in cosmetics. U.S. Pat. No. 6,187,323, for example, describes pharmaceutical and cosmetic compositions comprising a mixture of a gelled oil and an aqueous gel. The oil may be gelled with ethylcellulose by heating to 140° C. to dissolve the ethylcellulose. WO2008/081175 also describes an aqueous composition containing an active agent for cosmetic and pharmaceutical applications. This composition is a homogeneous mixture (not emulsion) of an oil component with an aqueous component. The oil component is gelled with ethylcellulose at 120° C. or 150° C. prior to mixing with the aqueous component. The aqueous component is gelled with a conventional cosmetic gelling agent. Aqueous gels such as these, however, do not provide the properties of the anhydrous semi-solid hydrophobic petroleum jelly.
M. A. Ruiz-Martinez et al. in Il Farmaco, 58 (2003) 1289-1294 describe compositions formed by dispersing ethylcellulose with certain polyethylene glycol (PEG)—olivate ester surfactants in olive oil at 100° C. Compositions with varying amounts of ethylcellulose, prepared at different temperatures with different surfactants, were made to find a composition suitable for use in drug delivery. The compositions were determined to be unable to recover structurally following shear stress, i.e., were not thixotropic. More importantly, PEG is a petroleum-based compound, and depending on manufacturing processes, PEGs may be contaminated with measurable amounts of 1,4-dioxane, a possible human carcinogen that doesn't easily degrade. Although 1,4-dioxane can be removed from cosmetics during the manufacturing process by vacuum stripping, there is no easy way for consumers to know whether products containing PEGs have undergone this process. PEGs themselves have also shown some evidence of genotoxicity and, if used on broken skin, can cause irritation and systemic toxicity.
U.S. Pat. No. 5,908,631 describes alcohol-free compositions for topical use in which ethylcellulose is solubilized in a solvent such as a natural oil, a trigyceride, a propylene glycol ester, a neopentyl glycol ester, or a fatty alcohol. Propylene glycol esters are made from propylene and fatty acids. Propylene glycol is produced by hydrochlorination of propylene. Propylene (or Propene) is produced from non-renewable fossil fuels—petroleum, natural gas and, to a much lesser extent, coal. Propene is a byproduct of oil refining and natural gas processing. Ethylene, propene, and other compounds are produced by cracking larger hydrocarbon molecules. Propene is separated by fractional distillation from hydrocarbon mixtures obtained from cracking and other refining processes. Neopentyl glycol (IUPAC name 2,2-dimethyl-1,3-propanediol) is an organic chemical compound. It is used in the synthesis of polyesters, paints, lubricants and plasticizers. Neopentyl glycol is synthesized industrially by the aldol reaction of formaldehyde and isobutyraldehyde. This creates the intermediate hydroxypivaldehyde, which can be converted to neopentyl glycol with either excess formaldehyde or catalytic hydrogenation of the aldehyde group to an alcohol group. Thus, this composition is definitely not hydrocarbon-free.
In view of the foregoing, it would be desirable to develop a novel non-hydrocarbon-based composition having more desirable rheological properties.